Processes for preparing color stable red-emitting phosphor particles having small particle size

ABSTRACT

A process for preparing a Mn+4 doped phosphor of formula IAx[MFy]:Mn+4   Iincludes combining a first solution comprising a source of A and a second solution comprising H2MF6 in the presence of a source of Mn, to form the Mn+4 doped phosphor; whereinA is Li, Na, K, Rb, Cs, or a combination thereof;M is Si, Ge, Sn, Ti, Zr, Al, Ga, In, Sc, Y, La, Nb, Ta, Bi, Gd, or a combination thereof;x is the absolute value of the charge of the [MFy] ion;y is 5, 6 or 7; andwherein a value of a Hammett acidity function of the first solution is at least −0.9.Particles produced by the process may have a particle size distribution with a D50 particle size of less than 10 μm.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a non-provisional of and claims priority from U.S.provisional application, Ser. No. 62/433,358, filed Dec. 13, 2016, theentire disclosure of which is incorporated herein by reference.

BACKGROUND

Red-emitting phosphors based on complex fluoride materials activated byMn⁴⁺, such as those described in U.S. Pat. Nos. 7,358,542, 7,497,973,and 7,648,649, can be utilized in combination with yellow/green emittingphosphors such as YAG:Ce to achieve warm white light (CCTs <5000 K onthe blackbody locus, color rendering index (CRI) >80) from a blue LED,equivalent to that produced by current fluorescent, incandescent andhalogen lamps. These materials absorb blue light strongly andefficiently emit in a range between about 610 nm and 658 nm with littledeep red/NIR emission. Therefore, luminous efficacy is maximizedcompared to red phosphors that have significant emission in the deeperred where eye sensitivity is poor. Quantum efficiency can exceed 85%under blue (440-460 nm) excitation. In addition, use of the redphosphors for displays can yield high gamut and efficiency.

Processes for preparing the materials described in the patent andscientific literature are capable of producing particles having particlesize greater than 10 μm, typically with a broad particle sizedistribution. Examples include Paulusz, A. G., J. Electrochem. Soc.,942-947 (1973), U.S. Pat. Nos. 7,497,973, and 8,491,816. Synthesis ofK₂SiF₆:Mn⁴⁺ nanorods is described in Cryst Eng Comm, 2015, 17, 930-936,DOI: 10.1039/C4CE01907E, published online 26 Nov. 2014. However,materials such as nanrods with a high aspect ratio can cause problems inmanufacturing LED packaging. In addition, total internal reflectioninside a particle with a high aspect ratio may reduce efficiency. US20160244663 discloses K₂SiF₆:Mn⁴⁺ particles having a D₅₀ particle sizeranging from about 10 μm to about 40 μm and a span less than 1.1. Yetthere remains a need for processes for preparing the complex fluoridephosphors that can yield a product having a particle size of less than10 μm, preferably less than 5 μm, with a relatively narrow particle sizedistribution, with excellent performance in lighting and displayapplications.

BRIEF DESCRIPTION

Briefly, in one aspect, the present invention relates to processes forpreparing a Mn⁺⁴ doped phosphor of formula I

A_(x)[MF_(y)]:Mn⁺⁴   I

-   -   includes combining a first solution comprising a source of A and        a second solution comprising H₂MF₆ in the presence of a source        of Mn, to form the Mn⁺⁴ doped phosphor; wherein    -   A is Li, Na, K, Rb, Cs, or a combination thereof;    -   M is Si, Ge, Sn, Ti, Zr, Al, Ga, In, Sc, Y, La, Nb, Ta, Bi, Gd,        or a combination thereof;    -   x is the absolute value of the charge of the [MF_(y)] ion;        -   y is 5, 6 or 7; and            wherein a value of a Hammett acidity function of the first            solution is at least −0.9.

In another aspect, the present invention relates to Mn⁴⁺ doped phosphorsof formula I in the form of a monodisperse population of particles witha D₅₀ particle size of less than 10 μm, particularly less than 5 μm, andaspect ratio of about 3/1 or less.

In yet another aspect, the present invention relates to microemulsionmethods for preparing a coated phosphor having a core comprising aphosphor of formula I and a manganese-free shell comprising a metalfluoride compound disposed on the core. The method includes combining afirst microemulsion comprising a phosphor of formula I with a secondmicroemulsion comprising a precursor for a metal fluoride compound, andisolating the coated phosphor.

DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings, wherein:

FIG. 1 is a schematic cross-sectional view of a lighting apparatus inaccordance with one embodiment of the invention;

FIG. 2 is a schematic cross-sectional view of a lighting apparatus inaccordance with another embodiment of the invention;

FIG. 3 is a schematic cross-sectional view of a lighting apparatus inaccordance with yet another embodiment of the invention;

FIG. 4 is a cutaway side perspective view of a lighting apparatus inaccordance with one embodiment of the invention;

FIG. 5 is a schematic perspective view of a surface-mounted device (SMD)backlight LED.

FIG. 6 is a graph of the value of the Hammett acidity function of KF andKHF₂ solutions in 48 wt. % hydrofluoric acid

DETAILED DESCRIPTION

The Mn⁴⁺ doped phosphors of formula I are complex fluoride materials, orcoordination compounds, containing at least one coordination centersurrounded by fluoride ions acting as ligands, and charge-compensated bycounter ions as necessary. For example, in K₂SiF₆:Mn⁴⁺, the coordinationcenter is Si and the counterion is K. Complex fluorides are occasionallywritten as a combination of simple, binary fluorides but such arepresentation does not indicate the coordination number for the ligandsaround the coordination center. The square brackets (occasionallyomitted for simplicity) indicate that the complex ion they encompass isa new chemical species, different from the simple fluoride ion. Theactivator ion (Mn⁴⁺) also acts as a coordination center, substitutingpart of the centers of the host lattice, for example, Si. The hostlattice (including the counter ions) may further modify the excitationand emission properties of the activator ion.

In particular embodiments, the coordination center of the phosphor, thatis, M in formula I, is Si, Ge, Sn, Ti, Zr, or a combination thereof.More particularly, the coordination center may be Si, Ge, Ti, or acombination thereof. The counterion, or A in formula I, may be Na, K, ora combination thereof, more particularly K. Examples of phosphors offormula I include K₂[SiF₆]:Mn⁴⁺, K₂[TiF₆]:Mn⁴⁺, K₂[SnF₆]:Mn⁴⁺,Cs₂[TiF₆], Rb₂[TiF₆], Cs₂[SiF₆], Rb₂[SiF₆], Na₂[TiF₆]:Mn⁴⁺,Na₂[ZrF₆]:Mn⁴⁺, K₃[ZrF₇]:Mn⁴⁺, K₃[BiF₆]:Mn⁴⁺, K₃[YF₆]:Mn⁴⁺,K₃[LaF₆]:Mn⁴⁺, K₃[GdF₆]:Mn⁴⁺, K₃[NbF₇]:Mn⁴⁺, K₃[TaF₇]:Mn⁴⁺. Inparticular embodiments, the phosphor of formula I is K₂SiF₆:Mn⁴⁺.

The amount of manganese in the Mn⁴⁺ doped phosphors of formula I mayrange from about 1.2 mol % based on the total number of moles of Mn andSi (about 0.3 wt % based on total phosphor weight) to about 21 mol %(about 5.1 wt %), particularly from about 1.2 mol % (about 0.3 wt %) toabout 16.5 mol % (about 4 wt %). In particular embodiments, the amountof manganese may range from about 2 mol % (about 0.5 wt %) to 13.4 mol %(about 3.3 wt %), or from about 2 mol % to 12.2 mol % (about 3 wt %), orfrom about 2 mol % to 11.2 mol % (about 2.76 wt %), or from about 2 mol% to about 10 mol % (about 2.5 wt %), or from about 2 mol % to 5.5 mol %(about 1.4 wt %), or from about 2 mol % to about 3.0 mol % (about 0.75wt %).

The Mn⁺⁴ doped phosphors of the present invention comprise amonodisperse population of particles having a D₅₀ particle size of lessthan 10 μm, particularly, less than 5 μm, more particularly less than 1μm, even more particularly less than 200 nm, and even more particularlyless than 50 nm. The particles have an aspect ratio of less than orequal to 3/1. Aspect ratio is the ratio of the largest dimension of theparticle to the smallest dimension orthogonal to it. The aspect ratio ofthe phosphor particles of the present invention may vary from less thanor equal to 311, to near unity for a particle having a cubic ordodecahedron form. In addition, the phosphor may be free of hydroxide(OH) groups or carbon, or both hydroxide group-free and carbon-free. Thepresence of OH groups or organic material that contains C—H bonds may bedetected by FT-IR. In some embodiments, span of the particle sizedistribution is less than 1.1.

The Mn⁺⁴ doped phosphors of the present invention may be prepared bycombining a first solution comprising a source of A and a secondsolution comprising H₂MF₆ in the presence of a source of Mn. The valueof the Hammett acidity function Ho of the first solution is at least−0.9, particularly at least −0.5. The Hammett acidity function defines ascale of acidity of strong acids, particularly HF, using thespectroscopically determined concentration of an indicator. The value ofthe Hammett acidity function is given by equation (1):

$\begin{matrix}{H_{0} = {{pK_{{BH}^{+}}} + {\log\frac{\lbrack B\rbrack}{\left\lbrack {BH^{+}} \right\rbrack}}}} & (1)\end{matrix}$

where

[B] is the concentration of weak base B;

[BH⁺] is the concentration of the conjugate acid of weak base B; and

pK_(BH+) is the dissociation constant of the conjugate acid.

Examples of indicating weak bases that may be used to measure the valueof the Hammett acidity function of solutions used in the processes ofthe present invention include the basic indicators shown in Table A.

TABLE A Basic Indicator Basic Strength (pK_(BH) ⁺ ) 4-Phenylazoaniline2.8 4-(Phenylazo)diphenylamine 1.5 4-Nitroaniline 1.1 2-Nitroaniline−0.2 4-Chloro-2-nitroaniline −0.9 4-Nitrodiphenylamine −2.42,4-Dichloro-6-nitroaniline −3.2 4-Nitroazobenzene −3.32,6-Dinitro-4-methylaniline −4.3 2,4-Dinitroaniline −4.4N,N-Dimethyl-2,4,6-trinitroaniline −4.7 solution in conc. H₂SO₄ Chalcone−5.6 2-Benzoylnaphthalene −5.9 4-Benzoylbiphenyl −6.22-Bromo-4,6-dinitroaniline −6.6 Anthraquinone −8.12,4,6-Trinitroaniline, −9.3 solution in conc. H₂SO₄Methods for determining the value of the Hammett acidity function ofaqueous HF solutions are known. For example, the value of the Hammettacidity function of concentrated aqueous HF solutions has beendetermined by Hyman et al. (J. Am. Chem. Soc., 1957, 79 (14), pp3668-3671).

The concentration of the source of A in the first solution may be atleast 6M, particularly at least 7.8M. The solvent for the first andsecond solutions may be aqueous HF, for example 48% HF in water. In someembodiments, the first solution is free of HF. In the HF-free solutions,the solvent may be water, a non-solvent or antisolvent for the phosphorproduct, or a combination thereof. Suitable materials that arenon-solvents or antisolvents include acetone, acetic acid, isopropanol,ethanol, methanol, acetonitrile, dimethyl formamide, and combinationsthereof.

The molar ratio of A to M may be at least 5/1, and in particularembodiments may be at least 7/1, or at least 8/1, or at least 9/1. Thatis, the ratio of the total number of moles of the source of A in thefirst solution to the total number of moles of H₂MF₆ in the secondsolution may be at least 5/1, and in particular embodiments may be atleast 7/1, 7/1, or at least 8/1, or at least 9/1.

The processes according to the present invention may be batch orcontinuous processes. For batch processes, the second solution iscombined with at least 50% by volume of the first solution, particularlyat least 75% by volume, over a period of less than 30 seconds,preferably less than 10 seconds, more preferably less than about 5seconds. For continuous processes, the first solution and the secondsolution are gradually added to a reactor in the presence of a source ofMn to form a product liquor. The value of Hammett acidity function ofthe first solution is at least −1.3, of the second solution is at least−3, and the volume ratio of 35% H₂SiF₆ to 49% HF in the second solutionis at least 1:2.5. In particular, the ratio is at least 1:2.2. Duringthe addition, the product liquor is gradually discharged from thereactor while maintaining a constant volume, particularly a volume ofless than 100 ml. US 2016/0244663 describes continuous processes forpreparing the phosphors of formula I. In some embodiments, the reactormay be precharged with a material selected from HF, a source of A,preformed particles of the Mn⁺⁴ doped phosphor or the undoped hostmaterial, or a combination thereof.

The second solution includes a source of M and may additionally includeaqueous HF. The source of M may be a compound containing Si, having goodin solubility in the solution, for example, H₂SiF₆, Na₂SiF₆, (NH₄)₂SiF₆,Rb₂SiF₆, Cs₂SiF₆, SiO₂ or a combination thereof, particularly H₂SiF₆.Use of H₂SiF₆ is advantageous because it has very high solubility inwater, and it contains no alkali metal element as an impurity. Thesource of M may be a single compound or a combination of two or morecompounds. The HF concentration in the first solution may be at least 15wt %, particularly at least 25 wt %, more particularly at least 30 wt %.Water may be added to the first solution, reducing the concentration ofHF, to decrease particle size and improve product yield. Concentrationof the material used as the source of M may be 25 wt %, particularly wt%.

The second solution may also include a source of Mn, and may alsoinclude aqueous HF as a solvent. Suitable materials for use as thesource of Mn include for example, K₂MnF₆, KMnO₄. K₂MnCl₆, MnF₄, MnF₃,MnF₂, MnO₂, and combinations thereof, and, in particular, K₂MnF₆Concentration of the compound or compounds used as the source of Mn isnot critical; and is typically limited by its solubility in thesolution. The HF concentration in the second solution may be at least 15wt %, particularly at least 30 wt %.

Amounts of the raw materials used generally correspond to the amounts ofeach component in the desired composition, except that an excess of thesource of A may be present. Flow rates may be adjusted so that thesources of M and Mn are added in a roughly stoichiometric ratio whilethe source of A is in excess of the stoichiometric amount. In manyembodiments, the source of A is added in an amount ranging from about150% to 300% molar excess, particularly from about 175% to 300% molarexcess. For example, in Mn-doped K₂SiF₆, the stoichiometric amount of Krequired is 2 moles per mole of Mn-doped K₂SiF₆, and the amount of KF orKHF₂ used may range from about 3.5 moles to about 6 moles of the productphosphor.

The source of A may be a single compound or a mixture of two or morecompounds. Suitable materials include KF, KHF₂, KC₆H₇O₇ (potassiumcitrate), KOH, KCl, KBr, KI, KHSO₄, KOCH₃, K₂S₂O₈, or K₂CO₃,particularly KF, KHF₂, potassium citrate, or a combination thereof, moreparticularly KF. A source of Mn that contains K, such as K₂MnF₆, may bea source of K, particularly in combination with KF, KHF₂, potassiumcitrate, or a combination thereof. The source of A may be present ineither or both of the first and second solutions, in a third solutionadded separately, in the reactor pot, or in a combination of one or moreof these.

One or both of the first and second solutions may additionally includeone or more chelating agents, for example, ammonium citrate, potassiumcitrate, iminodiacetic acid (IDA), and EDTA. In some embodiments, thefirst or second solution may contain potassium citrate as a source of A.Processes that include a chelating agent such as potassium citrate mayyield Mn⁴⁺ doped phosphor particles having a particle size distributionwith a D₅₀ particle size in the submicron range; particle size asmeasured by transmission electron microscopy (TEM) may be less than 1μm, particularly less than 200 nm, more particularly less than 50 nm.

One or both of the first and second solutions may additionally includeone or more surfactants. Surfactants suitable for use in the processesof the present invention include nonionic, anionic and cationicsurfactants, including, but not limited to, aliphatic amines such ascetyltrimethylammonium bromide (CTAB), fluorocarbon surfactants, stearicacid and stearate salts, and oleic acid and oleate salts. Suitablenonionic surfactants include polyoxyethylene sorbitan fatty acid esters,commercially available under the TWEEN® brand, fluorocarbon surfactantssuch as NOVEC™ ammonium fluoroalkylsulfonamide, available from 3M, andpolyoxyethylene nonylphenol ethers. Additional examples of suitablesurfactants are described in US 2015/0329770, U.S. Pat. No. 7,985,723and Kikuyama, et al., IEEE Transactions on Semiconductor Manufacturing,vol. 3, No. 3, August 1990, pp. 99-108.

In some embodiments, either or both of the first and second solutionsmay be a microemulsion. The microemulsion is composed of an organicphase and an aqueous phase, with at least one surfactant as anemulsifying agent. The organic phase may include one or more organicsolvents; suitable solvents include, but are not limited to, octanol,hexadecane, octadecane, octadecene, phenyldodecane, phenyltetradecane,or phenylhexadecane. The aqueous phase includes the sources of A, M, andMn described above and an aqueous solvent, for example, aqueous HF orH₂SiF₆. The microemulsion may additionally include one or morecosurfactants such as C₄-C₁₀ amines and alcohols, and/or one or morechelating agents. The proportions of the components of the solutions maybe adjusted so that they are above the critical micelle concentration.The microemulsion may be a reverse microemulsion composed of reversemicelles containing an aqueous solvent and the sources of A, M, and Mn,dispersed in an organic solvent. Microemulsion processes are capable ofproducing Mn⁴⁺ doped phosphor particles having a particle sizedistribution with a D₅₀ particle size in the submicron range; D₅₀particle size as measured by transmission electron microscopy (TEM) maybe less than 1 μm, particularly less than 200 nm.

After the product liquor is discharged from the reactor, the Mn⁺⁴ dopedphosphor may be isolated from the product liquor by simply decanting thesolvent or by filtration, and treated as described in U.S. Pat. Nos.8,252,613, 8,710,487, or U.S. Pat. No. 9,399,732, with a concentratedsolution of a compound of formula II in aqueous hydrofluoric acid;

Al¹ _(x)[MF_(y)]   II

wherein

A¹ is H, Li, Na, K, Rb, Cs, or a combination thereof;

M is Si, Ge, Sn, Ti, Zr, Al, Ga, In, Sc, Y, La, Nb, Ta, Bi, Gd, or acombination thereof;

x is the absolute value of the charge of the [MF_(y)] ion; and

y is 5, 6 or 7.

The compound of formula II includes at least the MF_(y) anion of thehost compound for the product phosphor, and may also include the A⁺cation of the compound of formula I. Fora product phosphor of formulaK₂SiF₆:Mn, suitable materials for the compound of formula II includeH₂SiF₆, Na₂SiF₆, (NH₄)₂SiF₆, Rb₂SiF₆, Cs₂SiF₆, or a combination thereof,particularly H₂SiF₆, K₂SiF₆ and combinations thereof, more particularlyK₂SiF₆ The treatment solution is a saturated or nearly saturated of thecompound of formula II in hydrofluoric acid. A nearly saturated solutioncontains about 1-5% excess aqueous HF added to a saturated solution.Concentration of HF in the solution ranges from about 25% (wt/vol) toabout 70% (wt/vol), in particular from about 40% (wt/vol) to about 50%(wt/vol). Less concentrated solutions may result in reduced performanceof the phosphor. The amount of treatment solution used ranges from about2-30 ml/g product, particularly about 5-20 ml/g product, moreparticularly about 5-15 ml/g product.

The treated phosphor may be vacuum filtered, and washed with one or moresolvents to remove HF and unreacted raw materials. Suitable materialsfor the wash solvent include acetic acid and acetone, and combinationsthereof.

Span is a measure of the width of the particle size distribution curvefor a particulate material or powder, and is defined according toequation (2):

$\begin{matrix}{{Span} = \frac{\left( {D_{90} - D_{10}} \right)}{D_{50}}} & (2)\end{matrix}$

wherein

-   -   D₅₀ is the median particle size for a volume distribution;    -   D₉₀ is the particle size for a volume distribution that is        greater than the particle size of 90% of the particles of the        distribution; and    -   D₁₀ is the particle size for a volume distribution that is        greater than the particle size of 10% of the particles of the        distribution.        Particle size of the phosphor powder may be conveniently        measured by laser diffraction or optical microscopy methods, and        commercially available software can generate the particle size        distribution and span. For phosphor particles of the present        invention, the D₅₀ particle size is less than 10 μm,        particularly less than 5 μm. Span of the particle size        distribution is not necessarily limited, and may be 1.0 in some        embodiments.

After the product phosphor is isolated from the product liquor, treatedand dried, it may be annealed to improve stability as described in U.S.Pat. No. 8,906,724. In such embodiments, the product phosphor is held atan elevated temperature, while in contact with an atmosphere containinga fluorine-containing oxidizing agent. The fluorine-containing oxidizingagent may be F₂, HF, SF₆, BrF₅, NH₄HF₂, NH₄F, KF, AlF₃, SbF₅, ClF₃,BrF₃, KrF₂, XeF₂, XeF₄, XeF₆, NF₃, SiF₄, PbF₂, ZnF₂, SnF₂, CdF₂ CdF₂, aC₁-C₄ fluorocarbon, or a combination thereof. Examples of suitablefluorocarbons include CF₄, C₂F₆, C₃F₈, CHF₃, CF₃CH₂F, and CF₂CHF. Inparticular embodiments, the fluorine-containing oxidizing agent is F₂.The amount of oxidizing agent in the atmosphere may be varied to obtaina color stable phosphor, particularly in conjunction with variation oftime and temperature. Where the fluorine-containing oxidizing agent isF₂, the atmosphere may include at least 0.5% F₂, although a lowerconcentration may be effective in some embodiments. In particular theatmosphere may include at least 5% F₂ and more particularly at least 20%F₂. The atmosphere may additionally include nitrogen, helium, neon,argon, krypton, xenon, in any combination with the fluorine-containingoxidizing agent. In particular embodiments, the atmosphere is composedof about 20% F₂ and about 80% nitrogen.

The temperature at which the phosphor is contacted with thefluorine-containing oxidizing agent is any temperature in the range fromabout 200° C. to about 700° C., particularly from about 350° C. to about600° C. during contact, and in some embodiments from about 500° C. toabout 600° C. The phosphor is contacted with the oxidizing agent for aperiod of time sufficient to convert it to a color stable phosphor. Timeand temperature are interrelated, and may be adjusted together, forexample, increasing time while reducing temperature, or increasingtemperature while reducing time. In particular embodiments, the time isat least one hour, particularly for at least four hours, moreparticularly at least six hours, and most particularly at least eighthours. After holding at the elevated temperature for the desired periodof time, the temperature in the furnace may be reduced at a controlledrate while maintaining the oxidizing atmosphere for an initial coolingperiod. The temperature may be reduced to about 200° C. with controlledcooling, then control may be discontinued if desired.

The manner of contacting the phosphor with the fluorine-containingoxidizing agent is not critical and may be accomplished in any waysufficient to convert the phosphor to a color stable phosphor having thedesired properties. In some embodiments, the chamber containing thephosphor may be dosed and then sealed such that an overpressure developsas the chamber is heated, and in others, the fluorine and nitrogenmixture is flowed throughout the anneal process ensuring a more uniformpressure. In some embodiments, an additional dose of thefluorine-containing oxidizing agent may be introduced after a period oftime.

The annealed phosphor may be treated with a saturated or nearlysaturated solution of a composition of formula II in aqueoushydrofluoric acid, as described above. The amount of treatment solutionused ranges from about 10 ml/g product to 20 ml/g product, particularlyabout 10 ml/g product. The treated annealed phosphor may be isolated byfiltration, washed with solvents such as acetic acid and acetone toremove contaminates and traces of water, and stored under nitrogen.

After treatment, the phosphor may be contacted with afluorine-containing oxidizing agent in gaseous form at a second, lowertemperature. The second temperature may the same as the firsttemperature, or may be less than the it, ranging up to and including225° C., particularly up to and including 100° C., and moreparticularly, up to and including 90° C. The time for contacting withthe oxidizing agent may be at least one hour, particularly at least fourhours, more particularly at least six hours, and most particularly atleast eight hours. In a specific embodiment, the phosphor is contactedwith the oxidizing agent for a period of at least eight hours at atemperature of about 90° C. The oxidizing agent may be the same as ordifferent from that used in the first annealing step. In particularembodiments, the fluorine-containing oxidizing agent is F₂. Moreparticularly, the atmosphere may include at least 20% F₂. The phosphormay be contained in a vessel having a non-metallic surface in order toreduce contamination of the phosphor with metals.

In another aspect, the present invention relates to microemulsionmethods for preparing coated phosphor particles that include a coatedphosphor having a core comprising a phosphor of formula I and amanganese-free shell comprising a metal fluoride compound disposed onthe core The materials may be prepared by distributing the phosphor offormula I or precursor(s) for the phosphor and precursor(s) for themetal fluoride among two or more microemulsions and then combining them.In particular embodiments, the precursor includes an element selectedfrom the group consisting of calcium, strontium, magnesium, barium,yttrium, scandium, lanthanum, and combinations thereof. Suitablesolvents for the organic phase include, but are not limited to, octanol,hexadecane, octadecane, octadecene, phenyldodecane, phenyltetradecane,or phenylhexadecane. The aqueous phase includes an aqueous solvent, forexample, aqueous HF or H₂SiF₆, in addition to the phosphor andprecursors. The microemulsion may additionally include one or morecosurfactants such as C₄-C₁₀ amines and alcohols, and/or one or morechelating agents. The proportions of the components of the solutions maybe adjusted so that they are above the critical micelle concentration.The microemulsion may be a reverse microemulsion composed of reversemicelles containing the aqueous phase dispersed in the organic phase. Inparticular embodiments, the metal fluoride compound is KMgF₃. A lightingapparatus or light emitting assembly or lamp 10 according to oneembodiment of the present invention is shown in FIG. 1. Lightingapparatus 10 includes a semiconductor radiation source, shown as lightemitting diode (LED) chip 12, and leads 14 electrically attached to theLED chip. The leads 14 may be thin wires supported by a thicker leadframe(s) 16 or the leads may be self-supported electrodes and the leadframe may be omitted. The leads 14 provide current to LED chip 12 andthus cause it to emit radiation.

The lamp may include any semiconductor blue or UV light source that iscapable of producing white light when its emitted radiation is directedonto the phosphor. In one embodiment, the semiconductor light source isa blue emitting LED doped with various impurities. Thus, the LED maycomprise a semiconductor diode based on any suitable III-V, II-VI orIV-IV semiconductor layers and having an emission wavelength of about250 to 550 nm. In particular, the LED may contain at least onesemiconductor layer comprising GaN, ZnSe or SiC. For example, the LEDmay comprise a nitride compound semiconductor represented by the formulaIn_(i)Ga_(j)Al_(k)N (where 0≤i; 0≤j; 0≤k, and i+j+k=1) having anemission wavelength greater than about 250 nm and less than about 550nm. In particular embodiments, the chip is a near-uv or blue emittingLED having a peak emission wavelength from about 400 to about 500 nm.Such LED semiconductors are known in the art. The radiation source isdescribed herein as an LED for convenience. However, as used herein, theterm is meant to encompass all semiconductor radiation sourcesincluding, e.g., semiconductor laser diodes. Further, although thegeneral discussion of the exemplary structures of the inventiondiscussed herein is directed toward inorganic LED based light sources,it should be understood that the LED chip may be replaced by anotherradiation source unless otherwise noted and that any reference tosemiconductor, semiconductor LED, or LED chip is merely representativeof any appropriate radiation source, including, but not limited to,organic light emitting diodes.

In lighting apparatus 10, phosphor composition 22 is radiationallycoupled to the LED chip 12. Radiationally coupled means that theelements are associated with each other so radiation from one istransmitted to the other. Phosphor composition 22 is deposited on theLED 12 by any appropriate method. For example, a water based suspensionof the phosphor(s) can be formed, and applied as a phosphor layer to theLED surface. In one such method, a silicone slurry in which the phosphorparticles are randomly suspended is placed around the LED. This methodis merely exemplary of possible positions of phosphor composition 22 andLED 12. Thus, phosphor composition 22 may be coated over or directly onthe light emitting surface of the LED chip 12 by coating and drying thephosphor suspension over the LED chip 12. In the case of asilicone-based suspension, the suspension is cured at an appropriatetemperature. Both the shell 18 and the encapsulant 20 should betransparent to allow white light 24 to be transmitted through thoseelements. Although not intended to be limiting, in some embodiments, themedian particle size of the phosphor composition ranges from about 1 toabout 50 microns, particularly from about 15 to about 35 microns.

In other embodiments, phosphor composition 22 is interspersed within theencapsulant material 20, instead of being formed directly on the LEDchip 12. The phosphor (in the form of a powder) may be interspersedwithin a single region of the encapsulant material 20 or throughout theentire volume of the encapsulant material. Blue light emitted by the LEDchip 12 mixes with the light emitted by phosphor composition 22, and themixed light appears as white light. If the phosphor is to beinterspersed within the material of encapsulant 20, then a phosphorpowder may be added to a polymer or silicone precursor, loaded aroundthe LED chip 12, and then the polymer precursor may be cured to solidifythe polymer or silicone material. Other known phosphor interspersionmethods may also be used, such as transfer loading.

In yet another embodiment, phosphor composition 22 is coated onto asurface of the shell 18, instead of being formed over the LED chip 12.The phosphor composition is preferably coated on the inside surface ofthe shell 18, although the phosphor may be coated on the outside surfaceof the shell, if desired. Phosphor composition 22 may be coated on theentire surface of the shell or only a top portion of the surface of theshell. The UV/blue light emitted by the LED chip 12 mixes with the lightemitted by phosphor composition 22, and the mixed light appears as whitelight. Of course, the phosphor may be located in any two or all threelocations or in any other suitable location, such as separately from theshell or integrated into the LED.

FIG. 2 illustrates a second structure of the system according to thepresent invention. Corresponding numbers from FIGS. 1-4 (e.g. 12 inFIGS. 1 and 112 in FIG. 2) relate to corresponding structures in each ofthe figures, unless otherwise stated. The structure of the embodiment ofFIG. 2 is similar to that of FIG. 1, except that the phosphorcomposition 122 is interspersed within the encapsulant material 120,instead of being formed directly on the LED chip 112. The phosphor (inthe form of a powder) may be interspersed within a single region of theencapsulant material or throughout the entire volume of the encapsulantmaterial. Radiation (indicated by arrow 126) emitted by the LED chip 112mixes with the light emitted by the phosphor 122, and the mixed lightappears as white light 124. If the phosphor is to be interspersed withinthe encapsulant material 120, then a phosphor powder may be added to apolymer precursor, and loaded around the LED chip 112. The polymer orsilicone precursor may then be cured to solidify the polymer orsilicone. Other known phosphor interspersion methods may also be used,such as transfer molding.

FIG. 3 illustrates a third possible structure of the system according tothe present invention. The structure of the embodiment shown in FIG. 3is similar to that of FIG. 1, except that the phosphor composition 222is coated onto a surface of the envelope 218, instead of being formedover the LED chip 212. The phosphor composition 222 is preferably coatedon the inside surface of the envelope 218, although the phosphor may becoated on the outside surface of the envelope, if desired. The phosphorcomposition 222 may be coated on the entire surface of the envelope, oronly a top portion of the surface of the envelope. The radiation 226emitted by the LED chip 212 mixes with the light emitted by the phosphorcomposition 222, and the mixed light appears as white light 224. Ofcourse, the structures of FIGS. 1-3 may be combined, and the phosphormay be located in any two or all three locations, or in any othersuitable location, such as separately from the envelope, or integratedinto the LED.

In any of the above structures, the lamp may also include a plurality ofscattering particles (not shown), which are embedded in the encapsulantmaterial. The scattering particles may comprise, for example, silica,alumina, zirconia, titania, or a combination thereof. The scatteringparticles effectively scatter the directional light emitted from the LEDchip, preferably with a negligible amount of absorption.

As shown in a fourth structure in FIG. 4, the LED chip 412 may bemounted in a reflective cup 430. The cup 430 may be made from or coatedwith a dielectric material, such as silica, alumina, zirconia, titania,or other dielectric powders known in the art, or be coated by areflective metal, such as aluminum or silver. The remainder of thestructure of the embodiment of FIG. 4 is the same as those of any of theprevious figures, and can include two leads 416, a conducting wire 432,and an encapsulant material 420. The reflective cup 430 is supported bythe first lead 416 and the conducting wire 432 is used to electricallyconnect the LED chip 412 with the second lead 416.

Another structure is a surface mounted device (“SMD”) type lightemitting diode 550, e.g. as illustrated in FIG. 5. This SMD is a“side-emitting type” and has a light-emitting window 552 on a protrudingportion of a light guiding member 554 and is particularly useful forbacklight applications. An SMD package may comprise an LED chip asdefined above, and a phosphor material that is excited by the lightemitted from the LED chip.

In some embodiments, the Mn^(4′) doped phosphors according to thepresent invention are used in direct emission display devices thatinclude arrays of microLEDs having dimensions on the scale of 1 to 300μm or, more specifically, 1 to 100 μm, and even the scale of 1 to 50 μm,1 to 20 μm, or 1 to 10 μm. Exemplary methods for fabricating directemission display devices that include phosphor particles in a wavelengthconversion layer coupled to the microLEDs are described in U.S. Pat. No.9,111,464, assigned to Lux Vue Technology Corporation, and U.S. Pat. No.9,627,437, assigned to Sharp Laboratories of America, Inc. Devices thatinclude a backlight unit or direct emission display according to thepresent invention include, but are not limited to, TVs, computers,smartphones, tablet computers and other handheld devices that have adisplay including a semiconductor light source; and a Mn⁴⁺ dopedphosphor according to the present invention.

When used with an LED emitting at from 350 to 550 nm and one or moreother appropriate phosphors, the resulting lighting system will producea light having a white color. Lamp 10 may also include scatteringparticles (not shown), which are embedded in the encapsulant material.The scattering particles may comprise, for example, silica, alumina,zirconia, titania, or a combination thereof. The scattering particleseffectively scatter the directional light emitted from the LED chip,preferably with a negligible amount of absorption.

Devices according to the present invention may include one or more otherlight emitting materials in addition to a Mn⁴⁺ doped phosphor. When usedin a lighting apparatus in combination with a blue or near UV LEDemitting radiation in the range of about 250 to 550 nm, the resultantlight emitted by the assembly may be a white light. Other phosphors orquantum dot (QD) materials, such as green, blue, yellow, red, orange, orother color phosphors or QD materials may be used in a blend tocustomize the color of the resulting light and produce specific spectralpower distributions. In other embodiments, the materials may bephysically separated in a multilayered structure, or may be present inone or more blends in a multilayered structure. In FIGS. 1-5, phosphorcomposition 22 may be a single layer blend or a multilayered structurecontaining one or more phosphors or QD materials in each layer. InmicroLED direct emission display devices, individual microLEDs may beseparately coupled to a Mn⁴⁺ doped phosphor and other phosphors orquantum dot (QD) materials to yield light having desired specifications.

Suitable phosphors for use in devices according to the presentinvention, along with a Mn⁴⁺ doped phosphor include, but are not limitedto:

((Sr_(1−z) (Ca, Ba, Mg, Zn)_(z))_(1−(x+w))(Li, Na, K,Rb)_(w)Ce_(x))₃(Al_(1−y)Si_(y))O_(4+y+3(x−w))F_(1−y−3(x−w)), 0<x≤0.10,0≤y≤0.5, 0≤z≤0.5, 0≤w≤x;(Ca, Ce)₃Sc₂Si₃O₁₂(CaSiG);(Sr,Ca,Ba)₃Al_(1−x)Si_(x)O_(4+x)F_(1−x):Ce³⁺ (SASOF));(Ba,Sr,Ca)₅(PO₄)₃(Cl,F,Br,OH):Eu²⁺,Mn²⁺;(Ba,Sr,Ca)BPO₅:Eu²⁺,Mn²⁺;(Sr,Ca)₁₀(PO₄)₆*nB₂O₃:Eu²⁺ (wherein 0≤n≤1); Sr₂Si₃O₈*2SrCl₂:Eu²⁺;(Ca,Sr,Ba)₃MgSi₂O₈:Eu²⁺,Mn²⁺;BaAl₈O₁₃:Eu²⁺; 2SrO*0.84P₂O₆*0.16B₂O₃:Eu²⁺;(Ba,Sr,Ca)MgAl₁₀O₁₇:Eu²⁺,Mn²⁺;(Ba,Sr,Ca)Al₂O₄:Eu²⁺; (Y,Gd,Lu,Sc,La)BO₃:Ce³⁺,Tb³⁺; ZnS:Cu⁺,Cl⁻;ZnS:Cu⁺,Al³⁺; ZnS:Ag⁺,Cl⁻;ZnS:Ag⁺,Al³⁺;(Ba,Sr,Ca)₂Si_(1−n)O_(4−2n):Eu²⁺ (wherein 0≤n≤0.2);(Ba,Sr,Ca)₂(Mg,Zn)Si₂O₇:Eu²⁺;(Sr,Ca,Ba)(Al,Ga,In)₂S₄:Eu²⁺;(Y,Gd,Tb,La,Sm,Pr,Lu)₃(Al,Ga)_(5−a)O_(12−3/2a):Ce³⁺ (wherein 0≤a≤0.5);(Ca,Sr)₈(Mg,Zn)(SiO₄)₄Cl₂:Eu²⁺,Mn²⁺; Na₂Gd₂B₂O₇:Ce³⁺,Tb³⁺;(Sr,Ca,Ba,Mg,Zn)₂P₂O₇:Eu²⁺,Mn²⁺;(Gd,Y,Lu,La)₂O₃:Eu³⁺,Bi³⁺; (Gd,Y,Lu,La)₂O₂S:Eu³⁺,Bi³⁺;(Gd,Y,Lu,La)VO₄:Eu³⁺,Bi³⁺;(Ca,Sr)S:Eu²⁺,Ce³⁺; SrY₂S₄:Eu²⁺; CaLa₂S₄:Ce³⁺;(Ba,Sr,Ca)MgP₂O₇:Eu²⁺,Mn²⁺;(Y,Lu)₂WO₆:Eu³⁺,Mo⁶⁺;(Ba,Sr,Ca)_(b)Si_(g)N_(m):Eu²⁺ (wherein 2b+4g=3m); Ca₃(SiO₄)Cl₂:Eu²⁺;(Lu,Sc,Y,Tb)_(2−u−v)Ce_(v)Ca_(1+u)Li_(w)Mg_(2−w)P_(w)(Si,Ge)_(3−w)O_(12−u/2)(where −0.5≤u≤1, 0≤v≤0.1, and 0≤w≤0.2);(Y,Lu,Gd)_(2−m)(Y,Lu,Gd)Ca_(m)Si₄N_(6+m)C_(1−m):Ce³⁺, (wherein 0≤m≤0.5);(Lu,Ca,Li,Mg,Y), α-SiAlON doped with Eu²⁺ and/or Ce³⁺;(Ca,Sr,Ba)SiO₂N₂:Eu²⁺,Ce³⁺;β-SiAlON:Eu²⁺, Ba[Li₂(Al₂Si₂)N₆]:Eu²⁺, 3.5MgO*0.5MgF₂*GeO₂:Mn⁴⁺;(Ca, Sr)_(1−c−f)Ce_(c)Eu_(f)Al_(1+c)Si_(1−c)N₃, (where 0≤c≤0.2,0≤f≤0.2);Ca_(1−h−r)Ce_(h)Eu_(r)Al_(1−h)(Mg,Zn)_(h)SiN₃, (where 0≤h≤0.2, 0≤r≤0.2);Ca_(1−2s−t)Ce_(s)(Li,Na)_(s)Eu_(t)AlSiN₃, (where 0≤s≤0.2, 0≤t≤0.2,s+t>0); (Sr, Ca)AlSiN₃: Eu²⁺,Ce³⁺ (CASN); (Ba, Sr)₂Si₅N₈:Eu²⁺;Sr[LiAl₃N₄]:Eu²⁺; and Sr[Mg₃SiN₄]:Eu²⁺.

QD materials for use in devices according to the present invention maybe a group II-VI compound, a group III V compound, a group IV-IVcompound, a group IV compound, a group I-III-VI₂ compound or acombination thereof. Examples of group II-VI compounds include CdSe,CdTe, CdS, ZnSe, ZnTe, ZnS, HgTe, HgS, HgSe, CdSeTe, CdSTe, ZnSeS,ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZnTe, CdHgS,CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, CdZnSeS, CdZnSeTe, CdZnSTe,CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe, HgZnSTe, or combinationsthereof. Examples of group III-V compounds include GaN, GaP, GaAs, AlN,AlP, AlAs, InN, InP, InAs, GaNP, GaNAs, GaPAs, AlNP, AlNAs, AlPAs, InNP,InNAs, InPAs, GaAlNP, GaAlNAs, GaAlPAs, GaInNP, GaInNAs, GaInPAs,InAlNP, InAlNAs, InAlPAs, and combinations therof. Examples of group IVcompounds include Si, Ge, SiC, and SiGe. Examples of group I-III-VI₂chalcopyrite-type compounds include CuInS₂, CuInSe₂, CuGaS₂, CuGaSe₂,AgInS₂, AgInSe₂, AgGaS₂, AgGaSe₂ and combinations thereof.

The QD materials may be a core/shell QD, including a core, at least oneshell coated on the core, and an outer coating including one or moreligands, preferably organic polymeric ligands. Exemplary materials forpreparing core-shell QDs include, but are not limited to, Si, Ge, Sn,Se, Te, B, C (including diamond), P, Co, Au, BN, BP, BAs, AlN, AlP,AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, InSb, AlN, AlP, AlAs,AlSb, GaN, GaP, GaAs, GaSb, ZnO, ZnS, ZnSe, ZnTe, CdS, CdSe, CdSeZn,CdTe, HgS, HgSe, HgTe, BeS, BeSe, BeTe, MgS, MgSe, MnS, MnSe, GeS, GeSe,GeTe, SnS, SnSe, SnTe, PbO, PbS, PbSe, PbTe, CuF, CuCl, CuBr, Cul,Si₃N₄, Ge₃N₄, Al₂O₃, (Al, Ga, In)₂(S, Se, Te)₃, Al₂CO, and appropriatecombinations of two or more such materials. Exemplary core-shell QDsinclude, but are not limited to, CdSe/ZnS, CdSe/CdS, CdSe/CdS/ZnS,CdSeZn/CdS/ZnS, CdSeZn/ZnS, InP/ZnS, PbSe/PbS, PbSe/PbS, CdTe/CdS andCdTe/ZnS.

The QD materials typically include ligands conjugated to, cooperatedwith, associated with, or attached to their surface. In particular, theQDs may include a coating layer comprising ligands to protect the QDsfrom environmental conditions including elevated temperatures, highintensity light, external gasses, and moisture, control aggregation, andallow for dispersion of the QDs in the matrix material.

In particular, phosphor composition 22 may include one or more phosphorsthat result in a green spectral power distribution under ultraviolet,violet, or blue excitation. In the context of the present invention,this is referred to as a green phosphor or green phosphor material. Thegreen phosphor may be a single composition or a blend that emits lightin a green to yellow-green to yellow range, such as cerium-doped yttriumaluminum garnets, more particularly (Y,Gd,Lu,Tb)₃(Al,Ga)₅O₁₂:Ce³⁺. Thegreen phosphor may also be a blend of blue- and red-shifted garnetmaterials. For example, a Ce³⁺-doped garnet having blue shifted emissionmay be used in combination with a Ce³⁺-doped garnet that has red-shiftedemission, resulting in a blend having a green spectral powerdistribution. Blue- and red-shifted garnets are known in the art. Insome embodiments, versus a baseline Y₃Al₅O₁₂:Ce³⁺ phosphor, ablue-shifted garnet may have Lu³⁺ substitution for Y³⁺, Ga³⁺substitution for Al³⁺, or lower Ce³⁺ doping levels in a Y₃Al₅O₁₂:Ce³⁺phosphor composition. A red-shifted garnet may have Gd³⁺/Tb³⁺substitution for Y³⁺ or higher Ce³⁺ doping levels. An example of a greenphosphor that is particularly useful for display applications isβ-SiAlON. In some embodiments, lighting apparatus 10 has a colortemperature less than or equal to 4200° K, and the only red phosphorpresent in phosphor composition 22 is the Mn⁴⁺ doped phosphor; inparticular, K₂SiF₆:Mn⁴⁺. The composition may additionally include agreen phosphor. The green phosphor may be a Ce³⁺-doped garnet or blendof garnets, particularly a Ce³⁺-doped yttrium aluminum garnet, and moreparticularly, YAG having the formula (Y,Gd,Lu,Tb)₃(Al,Ga)₅O₁₂:Ce³⁺. Whenthe red phosphor is K₂SiF₆:Mn⁴⁺, the mass ratio of the red phosphor tothe green phosphor material may be less than 3.3, which may besignificantly lower than for red phosphors of similar composition, buthaving lower levels of the Mn dopant.

The ratio of each of the individual phosphors in a phosphor blend mayvary depending on the characteristics of the desired light output. Therelative proportions of the individual phosphors in the variousembodiment phosphor blends may be adjusted such that when theiremissions are blended and employed in an LED lighting device, there isproduced visible light of predetermined x and y values on the CIEchromaticity diagram, and a white light is preferably produced. Thiswhite light may, for instance, may possess an x value in the range ofabout 0.20 to about 0.55, and a y value in the range of about 0.20 toabout 0.55. However, the exact identity and amounts of each phosphor inthe phosphor composition can be varied according to the needs of the enduser. For example, the material can be used for LEDs intended for liquidcrystal display (LCD) backlighting. In this application, the LED colorpoint would be appropriately tuned based upon the desired white, red,green, and blue colors after passing through an LCD/color filtercombination. The list of potential phosphor for blending given here isnot meant to be exhaustive and these Mn⁴⁺-doped phosphors can be blendedwith various phosphors with different emission to achieve desiredspectral power distributions.

Other materials suitable for use in devices according to the presentinvention include electroluminescent polymers such as polyfluorenes,preferably poly(9,9-dioctyl fluorene) and copolymers thereof, such aspoly(9,9′-dioctylfluorene-co-bis-N,N′-(4-butylphenyl)diphenylamine)(F8-TFB); poly(vinylcarbazole) and polyphenylenevinylene and theirderivatives. In addition, the light emitting layer may include a blue,yellow, orange, green or red phosphorescent dye or metal complex, or acombination thereof. Materials suitable for use as the phosphorescentdye include, but are not limited to, tris(1-phenylisoquinoline) iridium(III) (red dye), tris(2-phenylpyridine) iridium (green dye) and Iridium(III) bis(2-(4,6-difluorephenyl)pyridinato-N,C2) (blue dye).Commercially available fluorescent and phosphorescent metal complexesfrom ADS (American Dyes Source, Inc.) may also be used. ADS green dyesinclude ADS060GE, ADS061GE, ADS063GE, and ADS066GE, ADS078GE, andADS090GE. ADS blue dyes include ADS064BE, ADS065BE, and ADS070BE. ADSred dyes include ADS067RE, ADS068RE, ADS069RE, ADS075RE, ADS076RE,ADS067RE, and ADS077RE.

The Mn⁴⁺ doped phosphors of the present invention may be used inapplications other than those described above. For example, the materialmay be used as a phosphor in a fluorescent lamp, in a cathode ray tube,in a plasma display device or in a liquid crystal display (LCD). Thematerial may also be used as a scintillator in an electromagneticcalorimeter, in a gamma ray camera, in a computed tomography scanner orin a laser. These uses are merely exemplary and not limiting.

EXAMPLES Example 1: Baseline Process (C070616ATGAT(205))

Solution A was prepared by slowly adding 15.6 g of KF to a polypropylenebeaker that contained 22.3 mL 49% HF. Caution as this process isexothermic. The solution was stirred magnetically for 5 minutes.Solution B was prepared by adding 13.4 mL of 35% H₂SiF₆ to 71 mL of 49%HF in a 500 mL polypropylene beaker. While the solution was stirredmagnetically at 300 RPM, 1.8 g of K₂MnF₆ was added.

The contents of beaker A were quickly poured into Solution B and theresulting suspension is stirred for 3 minutes. The stirring is stopped,the supernatant is decanted, and the slurry is vacuum filtered, andwashed for 15 minutes in a nearly saturated solution of K₂SiF₆ in 49%HF. After the 15 minute washing step, stirring is stopped, thesupernatant is decanted and the slurry is vacuum filtered, rinsed oncewith 75 mL glacial acetic acid and three times with 75 mL of acetone.The solid is dried for more than 30 minutes under vacuum and thenannealed at 540° C. for 8 hours under a 20% fluorine:80% nitrogenatmosphere. The annealed powder is sifted through 280 mesh and thenwashed in a nearly saturated solution of K₂SiF₆ in 49% HF for 30minutes. After the 30 minute washing step, stirring is stopped, thesupernatant is decanted and the slurry is vacuum filtered, rinsed oncewith 75 mL glacial acetic acid, three times with 75 mL of acetone andthen dried under vacuum.

Example 2: Solution A of Higher Concentration (C070616BTGAT(205))

Solution A was prepared by adding 23.8 g of KF to a polypropylene beakerthat contained 34 mL 49% HF. Caution as this process is exothermic. Thesolution was stirred magnetically for 5 minutes. Solution B was preparedby adding 13.4 mL of 35% K₂SiF₆ was added to 71 mL of 49% HF in a 500 mLpolypropylene beaker. While the solution was stirred magnetically at 300RPM, 1.8 g of K₂MnF₆ was added.

The contents of Solution A were quickly poured into Solution B and theresulting suspension was stirred for 3 minutes. The stirring wasstopped, the supernatant was decanted, and the slurry was vacuumfiltered, rinsed with acetic acid and acetone, washed for 15 minutes ina nearly saturated solution of K₂SiF₆ in 49% HF. After the 15 minutewashing step, stirring was stopped, the supernatant was decanted and theslurry was vacuum filtered, rinsed once with 75 mL glacial acetic acidand three times with 75 mL of acetone. The solid was dried for more than30 minutes under vacuum and then annealed at 540° C. for 8 hours under a20% fluorine:80% nitrogen atmosphere. The annealed powder was siftedthrough 280 mesh and then washed in a nearly saturated solution ofK₂SiF₆ in 49% HF for 30 minutes. After the 30 minute washing step,stirring was stopped, the supernatant was decanted and the slurry wasvacuum filtered, rinsed once with 75 mL glacial acetic acid, three timeswith 75 mL of acetone and then dried under vacuum.

Example 3: Solution A of Lower Concentration (C070616CTGAT(205))

Solution A was prepared by slowly adding 15.6 g of KF to a polypropylenebeaker that contained 44 mL 49% HF. Caution as this process isexothermic. The solution was stirred magnetically for 5 minutes.Solution B was prepared by adding 13.4 mL of 35% H₂SiF₆ to 71 mL of 49%HF in a 500 mL polypropylene beaker. While the solution was stirredmagnetically at 300 RPM, 1.8 g of K₂MnF₆ was added.

The contents of beaker A were quickly poured into beaker B and theresulting suspension is stirred for 3 minutes. The stirring is stopped,the supernatant is decanted, and the slurry is washed for 15 minutes ina nearly saturated solution of K₂SiF₆ in 49% HF. After the 15 minutewashing step, stirring is stopped, the supernatant is decanted and theslurry is vacuum filtered, rinsed once with 75 mL glacial acetic acidand three times with 75 mL of acetone. The solid is dried for more than30 minutes under vacuum and then annealed at 540° C. for 8 hours under a20% fluorine:80% nitrogen atmosphere. The annealed powder is siftedthrough 280 mesh and then washed in a nearly saturated solution ofK₂SiF₆ in 49% HF for 30 minutes. After the 30 minute washing step,stirring is stopped, the supernatant is decanted and the slurry isvacuum filtered, rinsed once with 75 mL glacial acetic acid, three timeswith 75 mL of acetone and then dried under vacuum.

Example 4: Slower Solution A Addition (C070616DTGAT(205))

Solution A was prepared by slowly adding 15.6 g of KF to a polypropylenebeaker that contained 22.3 mL 49% HF. Caution as this process isexothermic. The solution was stirred magnetically for 5 minutes.Solution B was prepared by adding 13.4 mL of 35% H₂SiF₆ was added to 71mL of 49% HF in a 500 mL polypropylene beaker. While the solution wasstirred magnetically at 300 RPM, 1.8 g of K₂MnF₆ was added.

The contents of beaker A were added dropwise into beaker B over oneminute and the resulting suspension is stirred for 3 minutes. Thestirring is stopped, the supernatant is decanted, and the slurry isvacuum filtered, and washed for 15 minutes in a nearly saturatedsolution of K₂SiF₆ in 49% HF. After the 15 minute washing step, stirringis stopped, the supernatant is decanted and the slurry is vacuumfiltered, rinsed once with 75 mL glacial acetic acid and three timeswith 75 mL of acetone. The solid is dried for more than 30 minutes undervacuum and then annealed at 540° C. for 8 hours under a 20% fluorine:80%nitrogen atmosphere. The annealed powder is sifted through 280 mesh andthen washed in a nearly saturated solution of K₂SiF₆ in 49% HF for 30minutes. After the 30 minute washing step, stirring is stopped, thesupernatant is decanted and the slurry is vacuum filtered, rinsed oncewith 75 mL glacial acetic acid, three times with 75 mL of acetone andthen dried under vacuum.

Example 5: Less Concentrated Solution A (C070616ETGAT(205))

Solution A was prepared by slowly adding 15.6 g of KF to a polypropylenebeaker that contained 34 mL 49% HF. Caution as this process isexothermic. The solution was stirred magnetically for 5 minutes.Solution B was prepared by adding 13.4 mL of 35% H₂SiF₆ was added to 71mL of 49% HF in a 500 mL polypropylene beaker. While the solution wasstirred magnetically at 300 RPM, 1.8 g of K₂MnF₆ was added.

The contents of beaker A were quickly poured into beaker B and theresulting suspension was stirred for 3 minutes. The stirring wasstopped, the supernatant was decanted, and the slurry was vacuumfiltered, and washed for 15 minutes in a nearly saturated solution ofK₂SiF₆ in 49% HF. After the 15 minute washing step, stirring wasstopped, the supernatant was decanted and the slurry was vacuumfiltered, rinsed once with 75 mL glacial acetic acid and three timeswith 75 mL of acetone. The solid was dried for more than 30 minutesunder vacuum and then annealed at 540° C. for 8 hours under a 20%fluorine:80% nitrogen atmosphere. The annealed powder was sifted through280 mesh and then washed in a nearly saturated solution of K₂SiF₆ in 49%HF for 30 minutes. After the 30 minute washing step, stirring wasstopped, the supernatant was decanted and the slurry was vacuumfiltered, rinsed once with 75 mL glacial acetic acid, three times with75 mL of acetone and then dried under vacuum.

Example 6: Greater Amount of Solution A (C081016ATGAT(215))

The procedure of Example 2 was used except that 50 mL of Solution Acontaining KF at a concentration of 7 g/10 ml was used.

Example 7: Greater Amount of Solution A (C081016BTGAT(215))

The procedure of Example 2 was used except that 75 mL of Solution Acontaining KF at a concentration of 7 g/10 ml was used.

Example 8: Solution B Added to Solution A (C091316ATGAT(219))

The procedure of Example 2 was used except that Solution B was dividedbetween two beakers and added to Solution A.

Example 9: 34 gKF into Si (C091316CTGAT(219))

The procedure of Example 2 was used except that Solution A was dividedbetween two beakers which were poured simultaneously.

Example 10: Surfactant in Solution B (C092716ATGAT(222))

The procedure of Example 2 was used except that 1.3 g Tween20 was addedto Solution B with stirring 1 minute before KF addition.

Example 11: Surfactant in Solutions A and B (C092716BTGAT(222))

The procedure of Example 9 was used except that 0.8 g Tween20 added toSolution A.

Example 12: Repeat of Example 2 (C092716CTGAT(222))

The procedure of Example 2 was repeated.

Example 13: Scale up (C093016TGAT(223))

Solution A was prepared by slowly adding 95 g of KF to a polypropylenebeaker that contained 136 mL 49% HF. Caution as this process isexothermic. The solution was stirred magnetically for 5 minutes.Solution B was prepared by slowly adding 53.4 mL of 35% H₂SiF₆ to 283 mLof 49% HF. While the solution was stirred magnetically at 300 RPM, 7.2 gof K₂MnF₆ was added.

The contents of solution A were quickly poured into solution B and theresulting suspension was stirred for 3 minutes. The stirring wasstopped, the supernatant was decanted, and the slurry was vacuumfiltered, rinsed with acetic acid and acetone, washed for 15 minutes ina nearly saturated solution of K₂SiF₆ in 49% HF. After the 15 minutewashing step, stirring was stopped, the supernatant was decanted and theslurry was vacuum filtered, rinsed once with 75 mL glacial acetic acidand three times with 75 mL of acetone. The solid was dried for more than30 minutes under vacuum and then annealed at 540° C. for 8 hours under a20% fluorine:80% nitrogen atmosphere. The annealed powder was siftedthrough 280 mesh and then washed in a nearly saturated solution ofK₂SiF₆ in 49% HF for 30 minutes. After the 30 minute washing step,stirring was stopped, the supernatant was decanted and the slurry wasvacuum filtered, rinsed once with 75 mL glacial acetic acid, three timeswith 75 mL of acetone and then dried under vacuum.

Example 14: Continuous Process (C051716DTGAT(222))

Solution A was prepared by slowly adding 50.7 g KHF+71.9 g C₂H₃KO₂ to195 mL 49% HF. Solution B was prepared by slowly adding 10.29 g K₂MnF₆to 185 mL 49% HF. Solution C was prepared by adding 50 mL 35% H₂SiF₆ to90 mL 49% HF. Solutions A, B, C were flowed into a reaction vessel at45, 43, 32 mL/min respectively. The vessel was stirred at 300 rpm andnuclei formed almost instantaneously. When the volume of the suspensionreached 50 mL, the stopcock was opened such that this 50 mL volume wasmaintained throughout the remainder of the reaction. The output from thereactor was collected in a beaker, particles are given time to settleand then decanted to a slurry. The slurry was vacuum filtered, rinsedwith acetic acid and acetone, washed for 15 minutes in a nearlysaturated solution of K₂SiF₆ in 49% HF. After the 15 minute washingstep, stirring was stopped, the supernatant was decanted and the slurrywas vacuum filtered, rinsed once with 75 mL glacial acetic acid andthree times with 75 mL of acetone. The solid was dried for more than 30minutes under vacuum and then annealed at 540° C. for 8 hours under a20% fluorine:80% nitrogen atmosphere. The annealed powder was siftedthrough 280 mesh and then washed in a nearly saturated solution ofK₂SiF₆ in 49% HF for 30 minutes. After the 30 minute washing step,stirring was stopped, the supernatant was decanted and the slurry wasvacuum filtered, rinsed once with 75 mL glacial acetic acid, three timeswith 75 mL of acetone and then dried under vacuum.

Example 15: Water in Solution A (C101416AT)

Solution A was prepared by slowly adding 23.8 g of KF to a polypropylenebeaker that contained 38 mL water. Caution as this process isexothermic. The solution was stirred magnetically for 5 minutes.Solution B was prepared by slowly adding 13.4 mL of 35% H₂SiF₆ to 71 mLof 49% HF in a 500 mL polypropylene beaker. While the solution wasstirred magnetically at 300 RPM, 1.8 g of K₂MnF₆ was added.

The contents of solution A were split evenly between two beakers andsimultaneously quickly poured into solution B and the resultingsuspension was stirred for 3 minutes. The stirring was stopped, thesupernatant was decanted, and the slurry was vacuum filtered, rinsedwith acetic acid and acetone, washed for 15 minutes in a nearlysaturated solution of K₂SiF₆ in 49% HF. After the 15 minute washingstep, stirring was stopped, the supernatant was decanted and the slurrywas vacuum filtered, rinsed once with 75 mL glacial acetic acid andthree times with 75 mL of acetone. The solid was dried for more than 30minutes under vacuum and then annealed at 540° C. for 8 hours under a20% fluorine:80% nitrogen atmosphere. The annealed powder was siftedthrough 280 mesh and then washed in a nearly saturated solution ofK₂SiF₆ in 49% HF for 30 minutes. After the 30 minute washing step,stirring was stopped, the supernatant was decanted and the slurry wasvacuum filtered, rinsed once with 75 mL glacial acetic acid, three timeswith 75 mL of acetone and then dried under vacuum.

Example 16: Water and Surfactant in Solution A (C101416BTGAT)

Solution A was prepared by slowly adding 23.8 g of KF to a polypropylenebeaker that contained 38 mL water+3 mL Novec™ 4200. Novec™ 4200 is ananionic fluorochemical surfactant in a 25% aqueous solution. Caution asthis process is exothermic. The solution was stirred magnetically for 5minutes. Solution A was prepared by slowly adding 13.4 mL of 35% H₂SiF₆to 71 mL of 49% HF in a 500 mL polypropylene beaker. While the solutionwas stirred magnetically at 300 RPM, 1.8 g of K₂MnF₆ was added.

The contents of solution A were split evenly into two beakers andsimultaneously quickly poured into solution B and the resultingsuspension was stirred for 3 minutes. The stirring was stopped, thesupernatant was decanted, and the slurry was vacuum filtered, rinsedwith acetic acid and acetone, washed for 15 minutes in a nearlysaturated solution of K₂SiF₆ in 49% HF. After the 15 minute washingstep, stirring was stopped, the supernatant was decanted and the slurrywas vacuum filtered, rinsed once with 75 mL glacial acetic acid andthree times with 75 mL of acetone. The solid was dried for more than 30minutes under vacuum and then annealed at 540° C. for 8 hours under a20% fluorine:80% nitrogen atmosphere. The annealed powder was siftedthrough 280 mesh and then washed in a nearly saturated solution ofK₂SiF₆ in 49% HF for 30 minutes. After the 30 minute washing step,stirring was stopped, the supernatant was decanted and the slurry wasvacuum filtered, rinsed once with 75 mL glacial acetic acid, three timeswith 75 mL of acetone and then dried under vacuum.

Example 17: Higher Mn

Solution A was prepared by adding 23.8 g of KF to a polypropylene beakerthat contained 34 mL 49% HF. Caution as this process is exothermic. Thesolution was stirred magnetically for 5 minutes. Solution B was preparedby adding 12.5 mL of 35% K₂SiF₆ to added to 76 mL of 49% HF in a 500 mLpolypropylene beaker. While the solution was stirred magnetically at 300RPM, 2.51 g of K₂MnF₆ was added.

The contents of beaker A were split evenly into two beakers andsimultaneously quickly poured into beaker B and the resulting suspensionwas stirred for 3 minutes. The stirring was stopped, the supernatant wasdecanted, and the slurry was vacuum filtered, rinsed with acetic acidand acetone, washed for 15 minutes in a nearly saturated solution ofK₂SiF₆ in 49% HF. After the 15 minute washing step, stirring wasstopped, the supernatant was decanted and the slurry was vacuumfiltered, rinsed once with 75 mL glacial acetic acid and three timeswith 75 mL of acetone. The solid was dried for more than 30 minutesunder vacuum and then annealed at 540 C for 8 hours under a 20%fluorine:80% nitrogen atmosphere. The annealed powder was sifted through280 mesh and then washed in a nearly saturated solution of K₂SiF₆ in 49%HF for 30 minutes. After the 30 minute washing step, stirring wasstopped, the supernatant was decanted and the slurry was vacuumfiltered, rinsed once with 75 mL glacial acetic acid, three times with75 mL of acetone and then dried under vacuum. QE of the phosphors wasdetermined in a silicone tape. The tapes were prepared by mixing 500 mgof the material to be tested with 1.50 g silicone (Sylgard 184). Themixture was degassed in a vacuum chamber for about 15 minutes. Themixture (0.70 g) was poured into a disc-shaped template (28.7 mmdiameter and 0.79 mm thick) and baked for 30 minutes at 90° C. Thesample was cut into squares of size approximately 5 mm×5 mm for testing.QE was measured at excitation wavelength of 450 nm and is reportedrelative to a reference sample of Mn⁴⁺ doped K₂SiF₆ with 0.68% Mn and aparticle size of 28 microns from a commercial source. Lifetime wasdetermined using an Edinburgh FS900 Spectrometer by fitting a singleexponential decay to the measured data between 1.4 ms and 67 ms afterexcitation. The amount of manganese incorporated in the phosphor wasdetermined by inductively coupled plasma mass spectrometry (ICP-MS), andis reported as weight %, based on total weight of the phosphor material.For Examples 1-8, and 10-13, particle size based on volume distributionwas measured using a Horiba LA-960 Laser Scattering Particle SizeDistribution Analyzer. Results are shown in Table 1.

TABLE 1 Ex. No. Sample code % Mn QE D10/50/90, μm TEM p.s. Lifetime (ms)R631 1 C070616ATGAT(205) 2.26 102.4% 8/12/18 8.341 2 C070616BTGAT(205)2.27 102.6% 4/7/14 8.358 3 C070616CTGAT(205) 2.46 102.3% 19/25/33 8.3554 C070616DTGAT(205) 1.88 89.2% 12/20/31 8.064 5 C070616ETGAT(205) 2.09101.2% 10/14/21 8.312 6 C081016ATGAT(215) 1.86 99.6% 6/8/15 8.395 36.2%7 C081016BTGAT(215) 1.89 94.6% 5/9/16 8.363 35.7% 8 C091316ATGAT(219)1.94 104.0% 6/9/16 8.402 34.0% 9 C091316CTGAT(219) 1.88 104.3% 8.42736.2% 10 C092716ATGAT(222) 1.84 100.0% 2/5/8 8.454 37.5% 11C092716BTGAT(222) 1.78 102.0% 3/5/9 8.465 37.4% 12 C092716CTGAT(222)1.82 102.7% 5/8/14 8.449 35.2% 13 C093016TGAT(223) 1.86 101%   5/9/168.434 34.2% 14 C051716DTGAT(222) 2.71 94 7.984 25.3% 15 C101416ATGAT 2.6na 16 C101416BTGAT 2.58 na 17 C062916TGAT(203) 3.31 99 6/11/18 8.3 26.418 GRC090817T <50 nm 20 S082517 <200 nm

For Examples 9 and 14-16, particle size based on a number distributionwas measured by an optical microscopy method. The sample powder in thecontainer was shaken before any powder extraction was performed. A smallspatula was used to extract a very small amount of powder from the vialand placed on a glass slide. A small drop of dispersion oil was placedon a glass cover slip and was carefully placed on the powder samples onthe slide. The dispersion oil has a numerical aperture of about 1.6 sothat the particles show up with good contrast during imaging. The coverslip was pressed with an eraser equipped pencil and rotated severaltimes in order to disperse the powder on the slide. Three individualslides are made with each sample of powder by extracting a small volumeof powder three different times (as opposed to making 3 slides from oneextraction of powder). Three to five areas for image analysis areselected from each slide in order to minimize sampling bias. The slidewas then placed on a high resolution camera equipped transmitted lightmicroscope. The sample was scanned at low magnifications in order tofind areas with the best dispersion (less agglomerates) and to ensurethat the full range of particles are captured. An appropriate objectivelens was selected that resolves the preponderance of particles on theslide. The limit of optical resolution was approximately 0.25 μm. Themicroscope was interfaced to a workstation equipped with Clemex Visionimage analysis software which permits the image acquisition, processing,and measurement of the particles on the slide. The actual projection ofthe particles are imaged using transmitted illumination and the area ofthat projection was what was measured with subsequent assumptions madeabout the shape. Most often a spherical shape was assumed in order togenerate volumetric data. Results are shown in Table 2.

TABLE 2 Particle Size Distribution, Number-based Example no. Mean p.s.,μm Std. dev. Min. p.s., μm Max. p.s., μm 13 6.2 4.2 0.4 20.1 14 3.7 1.30.2 8.2 15 3.1 1.2 0.4 8.3 16 3.7 1.9 0.4 12.3

Value of Hammett Acidity Function of Solutions

The value of the Hammett acidity function is calculated using equation(1):

$\begin{matrix}{H_{0} = {{pK_{{BH}^{+}}} + {\log\frac{\lbrack B\rbrack}{\left\lbrack {BH^{+}} \right\rbrack}}}} & (1)\end{matrix}$

whereH₀ is the value of the Hammett Acidity function[B]=concentration of weak base B[BH⁺]=concentration of conjugate acid of weak base BpK_(BH+)=dissociation constant of conjugate acid

The concentration of neutral base [B] and conjugated acid of the weakbase [BH+] are measured using the absorbance of these species in thetest solution. Absorbance of neutral base is proportional to theconcentration of neutral species and absorbance decreases with increasedprotonation of the base. The absorbance of neutral base will reduce tozero when all base species are protonated. The choice of the base forany given acid solution is made based on the ability of the acid topartially protonate the weak base. If the acid to strong that itcompletely protonates the weak base, another base with weaker strengthshould be chosen of the hammett's acidity measurements.

The experimental procedure is as follows: A known weight of the weakbase (B) was added to two different bottles (A & B). A known volume of areference solution (Ref1) that dissolves the base but does not protonatethe base was added to bottle A and allow the indicator to dissolve inthe solution. This reference solution was typically a weaker acid thanour test solution. Once the base was fully dissolved the absorbance ofthe solution (A_(Ref)) was measured using UV-Vis spectrometer. A knownvolume of the test solution was added to bottle B. Once the base wasfully dissolved the absorbance of the solution (A_(test)) was measuredusing UV-Vis spectrometer. Since the absorbance is proportional to theconcentration of the neutral base in the solution, the ratio of[BH⁺]/[B] for the test solution was calculated using equation (3):

$\begin{matrix}{\frac{\left\lbrack {BH^{+}} \right\rbrack}{\lbrack B\rbrack} = \frac{\left( {A_{Ref} - A_{test}} \right)}{A_{Ref}}} & (3)\end{matrix}$

where

A_(Ref)=Absorbance of reference solution at a specific wavelength

A_(test)=Absorbance of test solution at a specific wavelength

The values of [BH⁺]/[B] and base strength of the weak base are used tocalculate the hammett's acidity of the test solution using equation 1.

Results:

FIG. 6 shows the change in Hammett's acidity value as the concentrationof potassium salts is varied. It can be seen that acidity of KF or KHF₂solutions in 48 wt. % HF decreases with increasing concentrations.

The value of the Hammett acidity function of solutions of differentpotassium sources in 48 wt. % hydrofluoric acid is shown in Table 3.Acidity of equimolar K salts dissolved in 48% HF decreases in thefollowing order:

-   -   KHSO4>KHF2>KF>K2CO3>KOH

TABLE 3 Potassium Source Hammett's Acidity KHSO₄ −3.11 KHF₂ −2.05 KF−0.85 K₂CO₃ −0.11 KOH 1.25

The value of the Hammett acidity function of mixtures of solutions of 48wt. % hydrofluoric acid and 35 wt. % fluorosilicic acid are shown intable 4. As the amount of HF added to H₂SiF₆ increased, the acidityincreased and addition of water to H₂SiF₆ solution resulted in adecrease in acidity.

TABLE 4 Volume ratio of Molarity of Molarity of Hammett's H₂SiF₆ & HF[SiF₆]²⁻ HF Acidity H₂SiF₆:HF = 1:0 3.18 0.00 −2.48 H₂SiF₆:HF = 1:1 1.5913.73 −2.80 H₂SiF₆:HF = 1:2 1.06 18.31 −2.88 H₂SiF₆:HF = 1:3 0.80 20.60−2.95 H₂SiF₆:HF = 1:4 0.64 21.97 −2.99 H₂SiF₆:HF:H₂O = 1:2:1 0.80 13.73−1.93

Example 18: Preparation Using Potassium Citrate

Solution A was prepared by mixing 100 mL H₂O and 15 g potassium citratein a 250 mL polypropylene beaker. Solution B was prepared by mixing 6 mL35% H₂SiF₆ (aq), 12 ml 49% HF, and 0.8 g of K₂MnF₆. The contents ofSolution B were poured into Solution A. The resulting suspension wascentrifuged, supernatant decanted, resuspended in acetic acid, andcentrifuged. The supernatant was decanted, resuspended in acetone, andcentrifuged, and the decant/resuspend in acetone/centrifuge steps wererepeated. The product from each of the four centrifugations wascollected and vacuum dried. The emission spectra of the powder wasmeasured and was found to be identical to that of standard size PFS. TEManalysis showed that the particles were uniform, with particle size lessthan 50 nm.

Example 19: Microemulsion Method for Preparation of KMgF₃-coatedK₂SiF₆:Mn Phosphor

Two reverse microemulsions, denoted Microemulsions I and II, areprepared separately. Microemulsions I and II contain 10 g ofcetyltrimethylammonium bromide dissolved in 40 g of 2-octanol (weightratio is 1:4). This mixture is stirred magnetically for 1 h, and thenaqueous salt solution I [0.0025 mol (0.641 g) Mg(NO₃)₂*6H₂O and 0.003mol (0.3033 g) KNOB dissolved in 4.6 mL H₂O] and aqueous salt solutionII [0.01 mol (0.3704 g) NH₄F is dissolved in 4.6 mL H₂O] are pouredslowly into microemulsion I and II, respectively. The water content inthe microemulsions is 8.6% (w/w). These two microemulsions are stirredseparately for two hours, and then 3.6 g of K₂SiF₆:Mn phosphor is addedto microemulsion I. Microemulsion I and II are combined at roomtemperature and stirred for 5-15 min, and the product is then vacuumfiltered and rinsed three times with ethanol. The coated phosphor isthen dried under vacuum.

Examples 20-23: Microemulsion Preparation of K₂SiF₆ and K₂SiF₆:MnProcedure

Two separate beakers were used in the synthesis of nanoparticles. Inboth beakers, A and B, CTAB was dissolved in 2-octanol and stirred for 1hr. Then the other components of beakers A and B listed in Table 5 werecombined and added to the CTAB/octanol. The contents of beaker A wereadded to beaker B and the mixture was stirred until the reaction wascomplete. Then stirring was stopped and the contents settled. Thesupernatant was decanted and the product washed with ethanol. The asformed K₂SiF₆ was washed and decanted in ethanol (5X) until all theexcess CTAB and 2-octanol was washed off, leaving only nanoparticles andethanol.

TEM showed nicely formed particles having particle size in the 200-500nm range with some particles that were submicron in size, with particlesize less than about 200 nm.

TABLE 5 Beaker A Beaker B Example 20: K₂SiF₆ Nanoparticles 40 g2-Octanol 40 g 2-Octanol 10 g CTAB 10 g CTAB 0.5055 g KNO₃ 0.4454 NH₄Si₆4.6 mls H₂O 4.6 mls H₂O Example 21: K₂SiF₆:Mn Nanoparticles 40 g2-Octanol 40 g 2-Octanol 10 g CTAB 10 g CTAB 0.5055 g KNO₃ 0.4454NH₄SiF₆ 4.6 mls H₂O 4.6 mls H₂O 0.006 g K₂MnF₆ Example 22: K₂SiF₆:MnNanoparticles 40 g 2-Octanol 40 g 2-Octanol 10 g CTAB 10 g CTAB 0.3905 gKHF₂ 0.3602 H₂SiF₆ 0.006 g K₂MnF₆ 4.6 mls 49% HF 4.6 mls 49% HF Example23: K₂SiF₆:Mn Nanoparticles 40 g 2-Octanol 40 g 2-Octanol 10 g CTAB 10 gCTAB 0.3905 g KHF₂ 0.3602 H₂SiF₆ 0.006 g K₂MnF₆ 2.3 mls 49% HF 2.3 mls49% HF 2.3 mls acetic acid 2.3 mls acetic acid

Any numerical values recited herein include all values from the lowervalue to the upper value in increments of one unit provided that thereis a separation of at least 2 units between any lower value and anyhigher value. As an example, if it is stated that the amount of acomponent or a value of a process variable such as, for example,temperature, pressure, time and the like is, for example, from 1 to 90,preferably from 20 to 80, more preferably from 30 to 70, it is intendedthat values such as 15 to 85, 22 to 68, 43 to 51, 30 to 32 etc. areexpressly enumerated in this specification. For values which are lessthan one, one unit is considered to be 0.0001, 0.001, 0.01 or 0.1 asappropriate. These are only examples of what is specifically intendedand all possible combinations of numerical values between the lowestvalue and the highest value enumerated are to be considered to beexpressly stated in this application in a similar manner.

While only certain features of the invention have been illustrated anddescribed herein, many modifications and changes will occur to thoseskilled in the art. It is, therefore, to be understood that the appendedclaims are intended to cover all such modifications and changes as fallwithin the true spirit of the invention.

1.-15. (canceled)
 16. A Mn⁺⁴ doped phosphor of formula I comprising amonodisperse population of particles having a particle size distributioncomprising a D₅₀ particle size of less than 10 μm;A_(x)[Mf_(y)]:Mn⁺⁴   I wherein A is Li, Na, K, Rb, Cs, or a combinationthereof; M is Si, Ge, Sn, Ti, Zr, Al, Ga, In, Sc, Y, La, Nb, Ta, Bi, Gd,or a combination thereof; x is the absolute value of the charge of the[MF_(y)] ion; and y is 5, 6 or 7; and wherein an aspect ratio of aplurality of particles of the population is less than or equal to 3/1.17. A Mn⁺⁴ doped phosphor according to claim 16, wherein the D₅₀particle size is less than or equal to 5 μm.
 18. A Mn⁺⁴ doped phosphoraccording to claim 16, wherein the phosphor is OH-free.
 19. A Mn⁺⁴ dopedphosphor according to claim 16, wherein the phosphor is carbon-free. 20.A Mn⁺⁴ doped phosphor according to claim 16, of formula K₂SiF₆:Mn.
 21. Alighting apparatus comprising a Mn⁺⁴ doped phosphor according to claim16.
 22. A backlight device comprising a Mn⁺⁴ doped phosphor according toclaim
 16. 23. A direct emission display device comprising a Mn⁺⁴ dopedphosphor according to claim
 16. 24. A microemulsion method for preparinga coated phosphor having a core comprising a phosphor of formula I and amanganese-free shell comprising a metal fluoride compound disposed onthe core, the method comprisingA_(x)[MF_(y)]:Mn⁴⁺   (I) combining a first microemulsion comprising aphosphor of formula I with a second microemulsion comprising a precursorfor a metal fluoride compound; and isolating the coated phosphor;wherein A is Li, Na, K, Rb, Cs, or a combination thereof; M is Si, Ge,Sn, Ti, Zr, Al, Ga, In, Sc, Hf, Y, La, Nb, Ta, Bi, Gd, or a combinationthereof; x is an absolute value of a charge of the [MF_(y)] ion; and yis 5, 6 or
 7. 25. A microemulsion method according to claim 24, whereinthe phosphor of formula I is K₂SiF₆:Mn.
 26. A microemulsion methodaccording to claim 24, wherein the metal fluoride compound is KMgF3. 27.A microemulsion method according to claim 24, wherein the precursorcomprises an element selected from the group consisting of calcium,strontium, magnesium, barium, yttrium, scandium, lanthanum, andcombinations thereof.